What does Luke 2:41 mean?

Here, again, we see Jesus' earthly parents living in obedience to God's commands. They raised Him according to requirements given in the Old Testament (Luke 2:21, 22). One mandate was for capable Jews to make a pilgrimage to Jerusalem, three times a year, for certain festivals (Deuteronomy 16:16). Mary and Joseph continue this obedience as Jesus matures (Luke 2:40). Since all eligible males are supposed to make this trip, it's likely that Jesus' family is travelling in a relatively large group. Group travel would have factored into this famous incident in Jesus' life.

The Feast of Passover is Israel's remembrance of deliverance from slavery in Egypt. This is described in Exodus 12:43–49.